Interplanetary Updates: Philae and New Horizons

byPaul GilsteronJune 16, 2015

Given that the Philae lander has just come to life after seven months without communicating, it’s no wonder that the mood among everyone involved with Rosetta’s mission to comet 67P/Churyumov–Gerasimenko is exuberant. On the surface of the comet, conditions have been improving for Philae since March, meaning that with higher temperatures and better illumination, it was hoped that the lander might reactivate. That hope was realized on June 13 when Rosetta picked up 330 data packets from an earlier segment of the lander’s mission.

“We are still examining the housekeeping information at the Lander Control Centre in the DLR German Aerospace Center’s establishment in Cologne, but we can already tell that all lander subsystems are working nominally, with no apparent degradation after more than half a year hiding out on the comet’s frozen surface.”

ESA also reports that a second burst of lander data was received on June 14. Apparently over 8000 packets of additional status data are available in Philae’s memory, but controllers are not clear as to when the data were recorded. We do know that the internal temperature of the lander has risen to –5ºC, an indication that we’re moving toward enough sunlight to reach the operating temperatures needed for normal operations and electricity generation.

67P/Churyumov–Gerasimenko rotates about every twelve hours. Philae needs at least 19 watts to switch on its transmitter, and ESA’s Rosetta blog reports that power levels are at about the 13 W level at comet sunrise and reach 24 W later in the cometary day. We’re learning that the lander’s solar panels are apparently generating power for over 135 minutes in each period of illumination. The downloaded telemetry evidently extends over a full day-night cycle of the comet, which makes it possible to infer how and when the lander is receiving sunlight.

Remember that communications are being relayed through the Rosetta orbiter, which can contact the lander twice every 24 hours. Because Rosetta is currently in a 200 to 235 kilometer orbit that is not optimized for communications with the lander, a trajectory change will be needed. The new orbit, scheduled to begin at 2325 UTC today, would reduce the orbiter’s distance to about 180 kilometers and should enable better contact with Philae. Establishing reliable contact and optimizing it will allow a new phase of science investigations to begin.

New Horizons: Trajectory Tune-Up

We’re now inside the one month mark before arrival at Pluto/Charon, and the plucky New Horizons couldn’t have been sent on a more interesting trajectory. The plan is to take the spacecraft inside the orbits of all five of Pluto’s moons, an approach known to be feasible following multiple sets of observations dedicated to spotting potential hazards. New Horizons’ Long-Range Reconnaissance Imager (LORRI) camera performed the work, returning the long exposure images needed to search for rings, even smaller moons and dust in the system.

The upshot: No new moons and no rings. This update from the New Horizons team notes that if any rings do exist, they would have to be less than 1600 kilometers wide or reflecting less than one five-millionth of the incoming sunlight. Another hazard search begins June 15 — this is an ongoing process — and we’ll get the update on those results by June 25. The final far encounter phase — Approach Phase 3 — begins in the last week of June and ends a week before the spacecraft’s close approach to Pluto. Additional images for final navigation uses are part of this phase, as are measurements of the solar wind and high-energy particles on the approach.

Image: This “movie,” composed of images taken by New Horizons’ Long Range Reconnaissance Imager (LORRI), shows Pluto as it rotates about its axis. The images were taken May 28-June 3, 2015, from distances ranging from approximately 56 million kilometers to 48.5 million kilometers. Visible are dramatic variations in Pluto’s surface features as it rotates. When a very large, dark region near Pluto’s equator appears near the limb, it gives Pluto a distinctly, but false, non-spherical appearance. Pluto is known to be almost perfectly spherical from previous data. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

New Horizons performed a 45-second thruster burn to optimize its trajectory on June 14, a change of a mere 52 centimeters per second based on previous imaging. It’s mind-boggling for those of us who grew up with Pluto as little more than a seemingly unreachable speck at system’s edge to realize that New Horizons is now less than 35 million kilometers out. We’re headed for a close approach at a distance of roughly 12,500 kilometers above the surface.

The second installment of “New Horizons: Countdown to Pluto” airs today at 1130 EDT (1530 UTC) on NASA TV, with repeat showtimes at 1530 EDT (1930 UTC) and 1930 EDT (2330 UTC). In this installment, mission team members Alice Bowman, Cathy Olkin and Chris Hersman will be going through the latest news on mission operations and science.

Comments on this entry are closed.

Harry R RayJune 16, 2015, 9:34

As posted in a comment for a PREVIOUS post, CHARON “seems” to be showing some detail as well. BUT: Charon ALSO seems to be slightly out of round in the posted video. ASSUMING that the details are NOT artifacts of distortion (Charon is ALSO deemed to be perfectly round) could you post a SERIES of stills on a future post so that I (and others) can view them at leisure, instead of just the “quick peek” the video provides?

ASSUMING that the details are NOT artifacts of distortion (Charon is ALSO deemed to be perfectly round) could you post a SERIES of stills on a future post so that I (and others) can view them at leisure, instead of just the “quick peek” the video provides?

I’ll be posting a lot more from New Horizons as it comes in, so I’m sure some of the images the team makes available will fit the bill.

The context of the data packets is “Apparently over 8000 packets of additional status data are available in Philae’s memory, but controllers are not clear as to when the data were recorded. “

I interpret this to mean that the 8000 data packets are still held by Philae and so they know that they are available but not the content, which includes the timestamps. I’m guessing Philae ransmitted a signal that basically said “I’ve go a data set of 8000 packets, confirm readiness to receive”.

I interpret that to mean that they do not know when the data were recorded YET, but they will once they assemble more packets.

I would not expect a data packet to have a time stamp, I would expect the packet to have a sequence number and time to live. Once enough packets are collected and reassembled the log entries or data should have a time stamp.

It would be unconscionable to collect data without some kind of time stamp, but I don’t think the packet is the right place for that.

Wouldn’t it be extraordinary if we could see exoplanets with even this degree of resolution.

OT. I was reading somewhere that LCROSS was turned to earth to observe it from a distance to characterize glint of the oceans, so that this might be used to determine if exoplanets had oceans. Very cool.

It would be wonderful if this technique could bolster detection of Earth-like worlds and that subsequently we could start imaging them rather that getting fanciful artist renderings.

. It states that there was a course correction of about 52 centimeters per second to allow NH to make a correction to allow it to visit all the moon’s of Pluto. It wasn’t clear to me from the article that John Hopkins University was the one that actually did the course correction. Mr. Gilster could you tell us if Hopkins University is the ACTUAL group that does the trajectory computations and also too issues of commands to enact those corrections ? If not, could you tell us who EXACTLY is the group that does do these type of maneuvers ?

NASA’s New Horizons spacecraft will soon introduce us to this tiny, distant world

BY CHRISTOPHER CROCKETT

11:55 AM, JUNE 12, 2015

Tiny, far-flung Pluto is about to have a visitor — at least for a few hours.

On July 14, NASA’s New Horizons spacecraft will reach the dwarf planet and try to learn all it can about Pluto and its five known moons. Then the probe will leave Pluto behind, vanishing into the frigid darkness beyond the planets.

In its wake, New Horizons will introduce Earth to the last of the “classical planets.” Probes have flown past, orbited, crashed into or landed on every other world that orbits the sun. Now Pluto is getting its turn.

“This is the last picture show,” says Alan Stern, the mission’s leader. “It’s the capstone moment to the reconnaissance of the planets.”

Plans for visiting Pluto began in earnest in 1989. Several ideas for a mission came and went, but it was tough to justify flying to so remote a place. “I wasn’t entirely certain what to think about the New Horizons mission,” says Mike Brown, a planetary scientist at Caltech. “You learn by studying examples of things. If there was nothing else like Pluto, why go to this oddball?”

My comment on the above quote:

What an odd comment to make: There is nothing else like Pluto in the Sol system, so why explore it? That is the attitude of a professional astronomer and scientist? It’s weird, its unique, so don’t bother sending a probe to it? For me that is EXACTLY why one explores other worlds, especially if they are different from what we know so far.

If Philae had actually landed where it was supposed to, the probe would now be out of action because temperatures would be too high. But as it is in shadow, the scientists hope that Philae can pick up where it left off.

“Thanks to the shadow, we have the capability now to wake up and have a very long-term activity. Now we are in a position not only to wake up but to resume science to an extent that might go beyond our expectations,” Jean-Pierre Bibring, Philae lead scientist, told the briefing.

New Study Suggests Pluto’s Charon May Have Harbored Underground Oceans Long Ago

By Leonidas Papadopoulos

With less than four weeks remaining before NASA’s New Horizons spacecraft speeds through the Pluto system for humanity’s first-ever close-up reconnaissance of the distant planet and its assortage of moons, speculation runs rampant among scientists and the general public alike about what these mysterious worlds at the outer reaches of the Solar System might look like up close. In the absence of any hard evidence thus far, scientists can only make educated guesses about what we’ll actually see when New Horizons makes its long-awaited flyby of Pluto and its moons on July 14.

In one such study, a team of U.S. astronomers has argued about the possibility for the existence of cracks on the surface of Pluto’s biggest moon Charon, not unlike those that have been documented on the surface of Jupiter’s moon Europa. If such findings were indeed to be uncovered on Charon, they would provide strong evidence for the existence of past liquid water oceans on the interior of the faraway frigid moon.

One of the great revelations of planetary exploration has been that our Solar System is awash in water, from the dry plains of Mars to the interiors of various outer icy moons like Jupiter’s Europa and Ganymede and Saturn’s moon Enceladus. In addition, the presence of water has been confirmed even in the most unlikely of places, like the permanently shadowed crates at the south poles of Mercury and the Earth’s Moon, as well as on dwarf planets like Ceres, providing a paradigm shift in our views about the prevalence of this all-important molecule in our planetary backyard. But what about more distant places in the Solar System, like Pluto and Charon? Could we find any evidence for the existence of subterranean layers of liquid water, like those that are believed to exist on Europa and Enceladus?

“Our model predicts different fracture patterns on the surface of Charon depending on the thickness of its surface ice, the structure of the moon’s interior and how easily it deforms, and how its orbit evolved,” adds Rhoden. “By comparing the actual New Horizons observations of Charon to the various predictions, we can see what fits best and discover if Charon could have had a subsurface ocean in its past, driven by high eccentricity.”

At one stage, Voyager 1, launched in September 1977, might have been in a suitable position to reach Pluto in the spring of 1986, following its encounter with Saturn, but it was ultimately decided to utilize the spacecraft for a close-range flyby of the planet’s large moon, Titan, instead. By the time Voyager 1 left the Saturnian system in November 1980, its trajectory was bent northwards, “above” the plane of the ecliptic, toward an eventual entry into interstellar space. Years later, Dr. Ellis Miner of JPL told this author that the decision was an easy one to make.

“We didn’t even know that Pluto had a moon at that time, but it wouldn’t have made any difference,” he explained. “If we were making that choice today, I believe the choice would be the same.” Nor was it possible for Voyager 2—having encountered Uranus in January 1986 and Neptune in August 1989—to reach Pluto, for the tiny world was by that stage closer to the Sun and one-quarter of the way around the Solar System in its long orbit and consequently beyond reach.

This was a pity, for even with Voyager 1’s 1970s technology, significant advances could have been made in humanity’s knowledge of Pluto. Certainly, the spacecraft might have conducted mapping of both Pluto and Charon and would likely have detected the quartet of tiny moons—Nix, Hydra, Kerberos, and Styx—during closest approach.

“Voyager 1 would have brought a magnetometer and a more diverse array of space plasma instruments to bear on Pluto than we will,” explained New Horizons Principal Investigator (PI) Dr. Alan Stern in a historical overview paper. “But it’s more important that New Horizons has much more advanced mapping cameras and a far more capable radio science experiment to determine atmospheric pressure and temperature. We also carry a dust impact detector. Voyager did not have such a device to study Pluto’s environment.”

[Why wasn’t New Horizons equipped with a magnetometer? I thought that was standard issue science equipment on a deep space probe mission?]

On the other hand, the small world would have been better positioned in its orbit for imaging by Voyager 1. In the spring of 1986, it would have presented a surface which was oriented equator-on to the Sun, allowing Voyager 1 to fully map it. This was quite different to the high-latitude illumination to be seen by New Horizons, for which much of Pluto’s “winter” hemisphere will be in darkness, but at the same time Voyager 1’s memory storage was far lower than its 2006-launched descendent and the resulting data set would have correspondingly less. In precis, a Voyager 1 flyby would have produced—in the words of Dr. Stern—“many spectacular discoveries, but with less data-depth and diversity than New Horizons is likely to achieve.”

Of course, as we now know, a Voyager 1 encounter with Pluto never garnered significant support in the late 1970s. “Owing in part to the lower risk of the Titan flyby than a long cruise to Pluto, and also the higher scientific priority at the time of Titan, the Pluto option was not exercised” as a Voyager 1 objective, Dr. Stern noted. “Of course, at the time this decision was made, Pluto’s atmosphere, small satellites, complex surface composition and the entire Kuiper Belt all remained undiscovered.

By the time of the 1989 Voyager 2 flyby of Pluto-analog Triton, Pluto’s richness and context was beginning to be understood. This, combined with the fascinating results of Voyager 2’s Triton flyby that included a pathologically young surface, active geysers and an atmosphere, motivated interest … to successfully appeal to NASA in 1989 to begin Pluto mission studies.”

[The less one knows about an alien world, the more one should be inclined to want to learn as much as one can about it as soon as possible. Especially if that world seems to be very much out of place from its celestial brethren. But hey, that’s just me.]

The adventure continues: ESA today confirmed that its Rosetta mission will be extended until the end of September 2016, at which point the spacecraft will most likely be landed on the surface of Comet 67P/Churyumov-Gerasimenko.

Rosetta was launched in 2004 and arrived at the comet in August 2014, where it has been studying the nucleus and its environment as the comet moves along its 6.5-year orbit closer to the Sun. After a detailed survey, Rosetta deployed the lander, Philae, to the surface on 12 November. Philae fell into hibernation after 57 hours of initial scientific operations, but recently awoke and made contact with Rosetta again.

Rosetta’s nominal mission was originally funded until the end of December 2015, but at a meeting today, ESA’s Science Programme Committee has given formal approval to continue the mission for an additional nine months. At that point, as the comet moves far away from the Sun again, there will no longer be enough solar power to run Rosetta’s set of scientific instrumentation efficiently.

“This is fantastic news for science,” says Matt Taylor, ESA’s Rosetta Project Scientist. “We’ll be able to monitor the decline in the comet’s activity as we move away from the Sun again, and we’ll have the opportunity to fly closer to the comet to continue collecting more unique data. By comparing detailed ‘before and after’ data, we’ll have a much better understanding of how comets evolve during their lifetimes.”

The reason I love to read this blog is because of Paul’s wonderful and well-researched articles about interesting things. Plus, the intelligent discussion that often ensues in the comments section.

I hate to be rude, but I do not so much enjoy verbatim quotes of and links to other articles, interesting or not, in the comments section. They have a tendency to drown out the aforementioned intelligent discussion. Perhaps we could find a separate space for posting those? I hear Reddit is really good for that.

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For the last twelve years, this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image: Marco Lorenzi).

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